Fuel injection apparatus

ABSTRACT

In a fuel injection apparatus in which an air sensor deflected as a function of the intake air quantities maintains the air-tofuel ratio at a constant value and wherein the return force affecting the air sensor and opposing the deflecting force of the air flow is derived from pressurized liquid, the pressure of said liquid is varied by altering the energizing current of an electromagnet forming part of a pressure control valve.

United States Patent 1191 Knapp Oct. 16, 1973 FUEL INJECTION APPARATUS [56] References Cited [75] Inventor: Heinrich Knapp, UNITED STATES PATENTS Leonberg-sllberberg, Germany 3,713,430 1/1973 Knapp 123/119 R Assigneez Robert Bosch Stuttgart 3,703,888 Eckert 19 R Germany Primary Examiner-Laurence M. Goodridge [22] Flled: July 1972 Assistant ExaminerDennis Toth [21] Appl. No.: 268,643 Att0rney-Edwin E. Greigg [30] Foreign Application Priority Data ABSTRACT July 5, 1971 Germany P 21 33 435.0 In a fuel injection apparatus in which an air sensor deflected as a function of the intake air quantities main- 123/119 123/1 19 123/139 tains the air-to-fuel ratio at a constant value and 1 3/14 261/50 26l/5l, 261/39 R, wherein the return force affecting the air sensor and 261/39 D opposing the deflecting force of the air flow is derived [51] Int. Cl. F02d 1/00 from pressurized liquid, the pressure of said liquid is F 191d of Search 139 1 19 varied by altering the energizing current of an electro- 123/32 AB, 32 EA, 140 MC, 119 F; 261/50 A, 51, 39 R, 39 D magnet forming part of a pressure control valve.

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FUEL INJECTION APPARATUS BACKGROUND OF THE INVENTION This invention relates to a fuel injection apparatus for the continuous injection of fuel into the suction tube of an externally-ignited internal combustion engine. In the suction tube there is disposed an arbitrarily operable butterfly valve and, spaced therefrom, an air sensor which is deflected by the intake air as a function of the air quantities against a normally constant return force which, however, is variable as a function of engine parameters. The air sensor, by virtue of its deflection, displaces a movable member of a fuel metering and distributor valve disposed in the fuel path to ensure a desired air-to-fuel ratio. The return force is supplied at least partially by a pressurized liquid and the return force on the movable valve member is varied by means of an electromagnet, the electromagnetic force of which is variable by engine parameters.

In a fuel injection apparatus of the aforeoutlined type, as disclosed in Eckert et al US. application Ser. No. 92,345, filed Nov. 24, 1970, now US. Pat. No. 3,703,888, the armature of the electromagnet directly contacts a control plunger which is also exposed to said pressurized liquid and which is in engagement with the air sensor. Thus, the return force affecting the air sensor is varied as a function of the energizing current intensity which, in turn, characterizes at least one engine parameter. In an arrangement of this type frictional effects may lead to undesirable alterations in the resetting force. 7 I

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide an improved fuel injection apparatus of the aforeoutlined type which is free from disadvantageous frictional effects.

Briefly stated, according to the invention, the electromagnet controls the pressure of the liquid supplying the said return force. For this purpose, it is associated with a biasing means of a pressure regulating valve which controls the pressure of said liquid and means are provided to vary the valve bias by said electromagnet as a function of the intensity of the energizing current.

The invention will be better understood, as well as further objects and advantages become more apparent, from the ensuing detailed specification of a preferred, although exemplary, embodiment taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal sectional view of the fuel injection apparatus according to the preferred embodiment;

FIG. 2 is a diagram of a circuit for generating a control current as a function of engine parameters and FIG. 3 is a diagram illustrating the control pressure as a function of the angular position a of the butterfly valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning first to FIG. 1, in the fuel injection apparatus shown, the intake air enters into a suction tube portion 1 which comprises a conical portion 3 accommodating an air sensor 2. Therefrom the intake air flows through a coupling hose 4 into a suction tube portion 5 which contains an arbitrarily operable butterfly valve 6. Subsequently, the intake air is admitted to one or more cylinders (not shown) of an internal combustion engine. The air sensor 2 comprises a plate member disposed normal to the direction of air flow and deflectable thereby in the conical portion 3 as an approximately linear function of the air quantities passing through the suction tube. Assuming a constant return force affecting the air sensor 2 and a constant air pressure prevailing upstream of the air sensor 2, the air pressure prevailing between the air sensor 2 and the butterfly valve 6 remains constant.

The air sensor 2 directly controls a fuel metering and quantity distributor valve 7. For transmitting the motion of the air sensor 2 to the valve 7, there is provided alever 8 which is integral with the sensor plate and which is pivotally held at 9. The lever 8 has an integral nose 10 which is in contact with a movable valve component 11 to displace the same. The latter forms part of the fuel metering valve 7 and is shaped as a control plunger. The radial face 12 of the control plunger 11 disposed remote from the nose 10 is affected by pressurized liquid which serves as the return force for the air sensor 2.

The supply of fuel is effected by a fuel pump 16 which is driven by an electromotor l5 and which draws fuel from a fuel tank 17 and forces it to the fuel metering valve 7 through a conduit 18. From the conduit 18 there extends, back into the fuel tank 17, a return conduit 19 which contains a pressure limiting valve 20.

From the conduit 18 the pressurized fuel is admitted to a channel 21 provided in the housing of the fuel metering and distributor valve 7. The chanel 21 communicates with an annular groove 22 provided in the control plunger 11 and also, with a plurality of chambers 23 (only one shown), each bounded by a portion of a diaphragm 24. Dependent upon the position of the control plunger 11, a bounding or control edge 11a of the annular groove 22 covers to a greater or lesser extent a plurality of control slots 25 (only one shown), each of which, through a channel 26, leads to a chamber 27 separated from an associated chamber 23 by the diaphragm 24. From the chamber 27 the fuel is admitted through a channel 28 to an individual fuel injection valve (not shown) disposed in the suction tube in the vicinity of the associated engine cylinder. The diaphragm 24 serves as the movable part of a flat seat valve which, by means of a spring 29, is maintained in an open position when the uel injection apparatus is not in operation. The diaphragm boxes, each formed of a chamber 23, a chamber 27 and a portion of the diaphragm 24 separating these two chambers, ensure that independently from the flow passage section at the control slots 25, as determined by the position of the bounding edge 11a, that is, independently from the fuel quantities flowingto the fuel injection valves, the pressure drop at the fuel metering valve 22, 25 is maintained substantially at a constant value. In this manner it is ensured that the extent of displacement of the control plunger 11 and the metered fuel quantities are proportionate to one another.

During the pivotal motion of the lever 8, the sensor plate of the air sensor 2 is displaced in the conical portion 3 of the air intake tube, so that between the periphery of the plate and the inner wall of the conical portion 3 there occurs a change of the annular flow passage section. This change is proportionate to the extent the air sensor 2 deflects. With this precondition there is ensured a linear dependency of the extent of displacement of the air sensor 2 and the sliding motion'of the control plunger 11, so that to the air quantity flowing through the air intake tube there is continuously added a proportionate fuel quantity.

The pressurized liquid which exerts a constant resetting force on the control plunger 11 is fuel. For this purpose, from the conduit 18 there extends a conduit 32 which merges into a channel 35 which, in turn, is in hydraulic communication with a pressure chamber 33 through a damping throttle 57. The chamber 33 accommodates that terminal portion of the control plunger 11 which includes the radial end face 12 disposed remote from the air sensor lever 8. The conduit 32 contains a throttle 34 which separates the supply circuit 18 of the fuel metering valve 7 from the control pressure circuit 32, 35. The fuel is admitted through the channel 35 to a pressure regulating valve assembly 36 and is returned therefrom through a return conduit 37 in a depressurized condition to the fuel tank 17. The pressure regulating valve 36 is designed as a flat seat valve in which the metallic diaphragm 24 serves as the movable valve member. When the pressure regulating valve 36 is in its open position, the diaphragm 24 clamped taut between a base 38 and a housing 39 determines, together with a stationary valve seat 40 forming an integral part of the base 38, the flow passage section of the pressure regulating valve. A very small deflection of the diaphragm 24 in a direction away from the valve seat 40 is sufficient to fully open the valve and to cause the fuel to flow in a depressurized condition through the annular flow passage of the valve 36 from the channel 35 through the return conduit 37 into the fuel tank 17. The diaphragm 24 separates two chambers 41 and 42 from one another and is loaded by a spring 43, the bias of which may be arbitrarily altered by means of a set screw 44. The spring 43 urges the diaphragm 24 into contact with the valve seat 40 (closed position of valve 36). The spring 43 is disposed in a bore 45 of a magnet core 46 and exerts its force on the diaphragm 24 through an armature 47 (which serves as a spring seat disc) and a force-transmitting member 48. On the core 46 there is mounted a solenoid 51. The armature 47 is suspended in a frictionless manner on a spider 52 which is held between the clamping members 53 and 54. The energizing current is applied to the solenoid 51 through a plug 55. The magnetic circuit is closed by a ring 56 surrounding the solenoid 51.

The aforedescribed fuel injection apparatus operates as follows:

When the internal combustion engine is running, the fuel pump 16 driven by the electromotor l draws fuel from the fuel tank 17 and forces it through the conduit 18 to the fuel metering valve 7. Simultaneously, the internal combustion engine draws air through the air intake tube 1, 3, 4, 5 and as a result, the air sensor 2 executes a certain deflection from its position of rest. As

a function of the extent of this deflection, the control plunger 11 is shifted by virtue of the pressure exerted In order to maintain the air-fuel mixture at a richer or leaner level dependent upon the operational condition of range of the internal combustion engine, the return force exerted on the air sensor Zhas to be altered as a function of engine parameters. This is effected by either measuring these parameters electronically or, after their conversion into electric magnitudes, varying them by means of an electric control apparatus. Then, as corresponding current intensities, they vary the intensity of the magnetic field of the solenoid 51. As a result, the armature 47, exposed to the magnetic field, opposes the force of the biasing spring 43 to a greater or lesser extent. Since the diaphragm 24 of the pressure regulating valve 36 requires only a minimum extent of displacement for controlling the pressure of the fuel in the channel 35 and thus the return force exerted on the radial face 12 of the control plunger 11 in the pressure chamber 33, the magnetic force, that is, the magnitude of the energizing current, may be converted directly into a pressure value. By supporting the armature 47 on the spider 52 and by virtue of designing the pressure control valve as a flat seat valve, the pressure regulating valve operates in a mechanically entirely frictionless manner. The magnetic hysteresis is maintained at a low value in a conventional manner by making the environmental components of nickel-containing iron.

As illustrated in FIG. 1, it is advantageous to integrate the pressure regulating valve 36 and the fuel metering and distributor valve 7 to simultaneously use the diaphragm 24 as the movable valve member for both valves and to maintain the control pressure conduits 32, 35 as short as possible. It is to be understood that the pressure regulating valve 36 may be arranged, in a manner not shown, separate from the fuel metering and distributor valve 7.

Turning now to FIG. 2, there is illustrated a diagram of an electric circuit for determining the magnitude of the energizing current applied to the electromagnet. This circuit may be of simple structure, because the requirements for accuracy are relatively low, since the entire desired alteration of the proportion A of air in the air-to-fuel ratio is only about 15 percent. Consequently, an error as large as 10 percent in the energizing current causes a deviation of only 1.5 percent in the control pressure.

The battery voltage is approximately stabilized by means of a zener diode 60 to which there is connected a series resistance 61. The circuit contains an RC component in order to obtain, immediately after the starting of the engine, a fuel enrichment which significantly decreases after approximately 20 seconds of running time. When the starter button 62 is actuated, the condenser C and the resistance R are short-circuited. This causes, during the starting operation and in accordance with the time constants of the RC component, a fuel enrichment which, following the course of an efunction, adjusts itself to the valve given by the resistances R and 63. Since the short-circuiting of the resistance R causes during the starting operation, a decrease of the resetting force affecting the air sensor 2, the latter may deflect to a greater extent and thus a rapid charging of the injection conduits with fuel becomes possible. The A -correction is effected by means of a grated plate 64 which is in contact with a slider 65 secured to the shaft 6aof the butterfly valve 6. The slider 65 is in contact withdifferent sectors of the grated plate for the different operational ranges of the engine. Thus, the grated plate has an idling sector 66, a California test sector 67, a high partial load sector 68 and a full load sector 69. According to the invention, the idling may be set at a potentiometer 70. To the sectors 68 and 69 there are connected respective resistances 71 and 72. For the warmup run of the engine, the control current is additionally increased by means of an NTC resistance 73. Other engine parameters (or, also, atmospheric pres sure valves for a height correction) may be fed into the circuit to affect the control voltage U The electric circuit illustrated in FIG. 2 further includes an amplifier 74, the input of which is connected to a temperature-independent resistance 75 and diodes 76 determining a certain threshold voltage. A follower-emitter transistor 77 is controlled by means of a voltage com parison in the amplifier 74 for determining the intensity of current flowing through the solenoid 51 of the electromagnet. Due to the emitter-follower circuit of the transistor 77, the temperature and thus the change of the resistance of the solenoid 51 has no effect on the energizing current flowing therethrough.

At high engine temperatures the resistance of the NTC resistance 73 is very small. In case the slider contact 65 is in its shown position which corresponds to a (the angular position of the butterfly valve 6) 5 (which is the range of the California test), the base of the transistor 77 is practically grounded and the control current is zero. In the other sectors 66, 68 or 69 of the grated plate 64 there are resistances 70, 71, 72 present to give rise to the desired control current. If, in case of a cold engine, the resistance of the NTC resistance 73 increases, the base voltage of the transistor 77 and thus the control current also increases, resulting in a corresponding fuel enrichment. The NTC resistance is connected into the circuit in such a conventional manner as to achieve linearization.

FIG. 3 illustrates a diagram of the course of the control pressure P as a function of the angular position a of the butterfly valve 6. The illustrated approximation in the shape of a stepped function is fully sufficient. The curve a illustrates the course of the control pressure in case of an operationally hot engine of operational (hot) temperatures, while the curve b shows the course of the control pressure during the warmup run of the engine.

During the warmup run of the engine, the control current of the electromagnet is additionally increased by means of the NTC resistance; consequently, the

control pressure of the pressurized liquid is decreased so that the entire control pressure curve corresponding to FIG. 3 as curve b is additionally lowered and thus a corresponding fuel enrichment is achieved.

What is claimed is:

1. In a fuel injection apparatus for the oontinuous injection of fuel into the suction tube of an internal combustion engine, said suction tube containing an arbitrarily operable butterfly valve, said apparatus being of the known type that has (a) an air sensor disposed in said sucion tube spaced from said butterfly valve, said air sesor being deflected by the flow of intake air as a function of the intake air quantities, (b) chamber means containing liquid, (0) means for pressurizing said liquid, (d) means for transmitting the force of said pressurized liquid to said air sensor, said force constituting a return force affecting said air sensor and opposing the deflecting force of the air flow, said return force being independent from the deflected position of said air sensor, (e) a fuel metering and distributor valve having a movable valve member operatively connected to said air sensor to be displaced thereby to an extent proportionate to the deflection of said air sensor for maintaining constant the fuel-to-air ratio for any given return force, (f) a pressure control valve varying, as a function of its position, the pressure of said liquid in said chamber means for altering said return force, the improvement comprising A. an electromagnet incorporated in said pressure control valve, said electromagnet including a solenoid,

B. circuit means for applying to said solenoid a current having an intensity characterizing at least one engine parameter and C. means responsive to the electromagnetic force of said solenoid for varying the position of said pressure control valve.

2. An improvement as defined in claim 1, said pressure control valve including a valve seat, a movable valve component cooperating therewith and spring means urging said valve component towards said valve seat into a closed position, said means responsive to the electromagnetic force of said solenoid affecting the force exerted on said movable valve component by said spring means.

3. An improvement as defined in claim 2, said valve seat of said pressure control valve having a planar configuration.

4. An improvement as defined in claim 3, said movable valve component of said pressure control valve being constituted by a diaphragm.

5. An improvement as defined in claim 2, including a movable spider member incorporated in said pressure control valve, said means responsive to said electromagnetic force including an armature affixed to said spider.

6. An improvement as defined in claim 1, said circuit means including A. a plate formed of a plurality of sectors insulated from one another, each sector having a different resistance value and B. a slider contact in engagement with a selected one of said sectors, said slider contact being affixed to said arbitrarily operable butterfly valve for engaging said selected sector and varying said current intensity as a function of the position of said butterfly valve.

7. An improvement as defined in claim 6, including means for ensuring a current intensity of zero for an angular position of said butterfly valve of between approximately 5 and 20.

8. An improvement as defined in claim 1, including means for varying said current intensity as a function of at least one temperature parameter.

9. An improvement as defined in claim 8, said circuit means including an NTC resistance for increasing said current intensity during the warmup run of the internal combustion engine.

10. An improvement as defined in claim 1, said circuit means including an RC component for increasing said current intensity for a short period of time immediately following the starting of the engine.

11. An improvement as defined in claim 1, said circuit means including a potentiometer for varying said current intensity to set said return force for the idling range of said engine. 

1. In a fuel injection apparatus for the continuous injection of fuel into the suction tube of an internal combustion engine, said suction tube containing an arbitrarily operable butterfly valve, said apparatus being of the known type that has (a) an air sensor disposed in said suction tube spaced from said butterfly valve, said air sensor being deflected by the flow of intake air as a function of the intake air quantities, (b) chamber means containing liquid, (c) means for pressurizing said liquid, (d) means for transmitting the force of said pressurized liquid to said air sensor, said force constituting a return force affecting said air sensor and opposing the deflecting force of the air flow, said return force being independent from the deflected position of said air sensor, (e) a fuel metering and distributor valve having a movable valve member operatively connected to said air sensor to be displaced thereby to an extent proportionate to the deflection of said air sensor for maintaining constant the fuel-to-air ratio for any given return force, (f) a pressure control valve varying, as a function of its position, the pressure of said liquid in said chamber means for altering said return force, the improvement comprising A. an electromagnet incorporated in said pressure control valve, said electromagnet including a solenoid, B. circuit means for applying to said solenoid a current having an intensity characterizing at least one engine parameter and C. means responsive to the electromagnetic force of said solenoid for varying the position of said pressure control valve.
 2. An improvement as defined in claim 1, said pressure control valve including a valve seat, a movable valve component cooperating therewith and spring means urging said valve component towards said valve seat into a closed position, said means responsive to the electromagnetic force of said solenoid affecting the force exerted on said movable valve component by said spring means.
 3. An improvement as defined in claim 2, said valve seat of said pressure control valve having a planar configuration.
 4. An improvement as defined in claim 3, said movable valve component of said pressure control valve being constituted by a diaphragm.
 5. An improvement as defined in claim 2, including a movable spider member incorporated In said pressure control valve, said means responsive to said electromagnetic force including an armature affixed to said spider.
 6. An improvement as defined in claim 1, said circuit means including A. a plate formed of a plurality of sectors insulated from one another, each sector having a different resistance value and B. a slider contact in engagement with a selected one of said sectors, said slider contact being affixed to said arbitrarily operable butterfly valve for engaging said selected sector and varying said current intensity as a function of the position of said butterfly valve.
 7. An improvement as defined in claim 6, including means for ensuring a current intensity of zero for an angular position of said butterfly valve of between approximately 5* and 20*.
 8. An improvement as defined in claim 1, including means for varying said current intensity as a function of at least one temperature parameter.
 9. An improvement as defined in claim 8, said circuit means including an NTC resistance for increasing said current intensity during the warmup run of the internal combustion engine.
 10. An improvement as defined in claim 1, said circuit means including an RC component for increasing said current intensity for a short period of time immediately following the starting of the engine.
 11. An improvement as defined in claim 1, said circuit means including a potentiometer for varying said current intensity to set said return force for the idling range of said engine. 